Has anyone connected the programming USB to one computer and the native USB to another? I'm developing a game controller and having the programming USB connected to one machine whilst the native is connected to the other computer which is running the game would be very helpful.

The power from the two USB ports goes through two MOSFETS before it reaches the 5v rail on the board. One of the MOSFETS is under the control of the chip: the notes on the schematic say that this is to switch off power to the native USB when in host mode.

Since you don't really know where the grounds of your two computers are, connecting them could cause flash-bang-smoke even if the 5v lines are isolated. If one of the computers is a laptop and you can run it on the battery - no connection to mains power - then that would be OK.

The power from the two USB ports goes through two MOSFETS before it reaches the 5v rail on the board. One of the MOSFETS is under the control of the chip: the notes on the schematic say that this is to switch off power to the native USB when in host mode.

Its not host mode that's the issue, its when you parallel the outputs of two 5V regulators youcan get oscillation (large voltage swings) I lost 5 chips on one board to this through carelessnessonce, its something you should never do.

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